1. Field of the Invention
The present invention relates to ink ribbon units and ink ribbon cassettes used in printers of thermally sublimate ink transferal type.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional ink ribbon cassette 100 will be described with reference to FIG. 10, which is used in a color printer of a thermally sublimate ink transferal type. The cassette 100 generally comprises a casing 101, feeding and winding spools 103 and 104 installed in the casing 101 and an ink ribbon 102 movably held by the spools 103 and 104. The feeding spool 103 holds an unused section of the ink ribbon 102, while, the winding spool 103 holds a used section of the ribbon 102.
The ink ribbon 102 has for example yellow ink, magenta ink and cyanine ink which are infiltrated therein at evenly spaced intervals.
In accordance with types of papers on which printing is carried out, various ink ribbon cassettes of the above-mentioned type are prepared. That is, each time the type of paper changes, an operator must change the cassette. Information (such as, number of colors, inking sensitivity, etc.,) on the ink ribbon 102 installed in the casing 101 is represented by projected/depressed marks provided on the casing 101. When the cassette 100 is inserted into the printer, an optical sensor of the printer senses the marks and thus reads the information on the ink ribbon which is ready for printing or inking. The ink ribbon cassette of this type is described in, for example, Japanese Patent First Provisional Publication 63-254085.
However, in the ink ribbon cassettes of the above-mentioned type, numerous optical sensors must be installed in the printer in order to judge the types of various ink ribbon cassettes. In fact, when using such cassettes, one optical sensor can judge only two types of cassettes and two optical sensors can judge only four types of cassettes. As is known, usage of numerous optical sensors not only increases the cost of the printer but also causes a bulky construction of the same.
In view of these drawbacks, a measure has been proposed by, for example, Japanese Patent First Provisional Publication 2-20368. In this measure, a plurality of information marks representing information (viz., the number of colors, the linking sensitivity, etc.,) on an ink ribbon in the cassette are provided on the feeding spool, not on the casing. When the cassette is put into the printer and the printer is switched ON, the winding spool is slightly turned in the direction to wind thereon the ink ribbon. With this, the feeding spool is turned in the direction to feed the ink ribbon, and thus, the information marks on the feeding spool revolve together with the feeding spool giving various information on the ink ribbon to a single optical sensor installed in the printer.
However, even the measure proposed by the 2-20368 Publication has the following drawbacks.
That is, reading the information on the ink ribbon is available only when the feeding spool is turned. However, this causes wasteful usage of the ink ribbon. In fact, a part of the unused section of the ink ribbon, which passes by a printing head of the printer under the information reading, can not contribute to the printing or inking. Furthermore, such wasteful feeding of the ink ribbon tends to produce a slack of the ink ribbon, which tends to have the unused section of the ink ribbon stained or damaged. This wasteful feeding of the ink ribbon is much severe when the feeding for the information reading takes place after the printer has been stopped in the middle of the printing.